xpath2eval

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Module

The xpath2eval accessor is exported by the urn:org:ten60:netkernel:ext:xquery module. Import this module to gain access to the accessor.

Syntax

URI

active:xpath2eval

Argument	Rules	Description
operand	Mandatory	the resource to be tested
operator	Mandatory	a canonical XPath
namespace	Optional	an optional namespace document to enable prefix resolution

Example Usage

DPML

<instr>
  <type>xpath2eval</type>
  <operand>foo.xml</operand>
  <operator>bar.xml</operator>
  <target>this:response</target>
</instr>

NetKernel Foundation API

req=context.createSubRequest("active:xpath2eval");
req.addArgument("operand", [resource representation, aspect, or URI] );
req.addArgument("operator", [resource representation, aspect, or URI] );
result=context.issueSubRequest(req);

Purpose

The xpath2eval accessor is used to perform a boolean test of an xpath v2.0 expression on the operand. The operator contains a canonical XPath expression to be evaluated on the operand.

This accessor uses the Saxon XPath 2.0 engine which complies with the W3C XPath 2.0 draft specification.

The truth of an XPath expression can include the document tree matches an xpath location, the value of a location matches a given value or an XPath function matches some value, or a combination of all of these.

xpath2eval returns a boolean aspect

namespace argument syntax

XPath2.0 doesn't support XQuery style 'declare namespace' declarations and so namespace prefixes have to be supplied separately to the XPath evaluation engine. The namespace argument can supply an optional document containing prefix-uri pairs. It has the following form...

<namespace>
  <default>an optional default namespace uri - this has no prefix</default>
  <entry>
    <prefix>the ns prefix</prefix>
    <uri>the ns uri</uri>
  </entry>
            ...as many entries as required...
        
</namespace>

Example

Test if an Attribute has a given value

<idoc>
  <instr>
    <type>xpath2eval</type>
    <operand>
      <test:a xmlns:test="http://1060.org/test">
        <b name="foo" />
      </test:a>
    </operand>
    <operator>
      <xpath>/*:a/b[@name='foo']</xpath>
    </operator>
    <target>this:response</target>
  </instr>
</idoc>

An example of using xpath2eval to test if the operand document has an element <b> with an attribute name with value 'foo'. This example shows how Xpath 2.0 now supports wildcard namespace matching